Lab 5 Department of Computer Science and Information Engineering National Taiwan University Lab5 ...

Lab 5 Department of Computer Science and Information EngineeringNational Taiwan University / 251

Computer System Laboratory

Lab5 – Bootloader + OS Kernel

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Experimental Goal Learn how to build U-Boot bootloader for PXA270. Learn how to build Linux kernel image for PXA270.

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Environment Host System

Windows XP Build System

VirtualBox + Ubuntu 8.04 Target System

Creator XScale PXA270 Software

DENX U-Boot Linux for PXA270 linux-2.6.15.3-creator-pxa270.patch mkimage utility Root filesystem image (15M)

You can find all software on CSL Course Software.

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http://140.112.90.160:5000/fbdownload/2015CSL?k=st83M7ge&stdhtml=true


Bootloader Concept A typical flow when booting a computer.

Load BIOS and do hardware self-test. Execute bootloader in master boot record (MBR) which is the first sector of disk. Load kernel and root filesystem. Initialize hardware. …

When a computer is powered on, CPU will execute the first instruction from a specified address: ROM, EEPROM, Flash memory, etc. In ARM system, the address usually is 0x00000000.

In other words, bootloader is usually located at 0x00000000. Typical space allocation:

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Bootloader Examples Bootloader highly depends on architecture. Some popular bootloaders:

LILO, GRUB, GRUB2 You can see /boot/grub/menu.lst for the settings in Ubuntu 8.04.

Windows Boot Manager You can see the settings in C:\boot.init in Windows XP.

U-Boot We will use U-Boot for PXA270 (ARM architecture).

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Introduction to U-Boot Das U-Boot (Universal Bootloader) is an open source, primary bootloader

used in embedded systems. It is available for a number of different computer architectures, including

PPC, ARM, MIPS, x86, etc. The current name Das U-Boot adds a German definite article as a pun to

the German word for “submarine”.

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Reference: Das U-Boot, http://en.wikipedia.org/wiki/Das_U-Boot

http://en.wikipedia.org/wiki/Das_U-Boot

http://en.wikipedia.org/wiki/Das_U-Boot


U-Boot Compilation (1/2) Step 1: download the patched source codes of U-Boot (mt-u-boot-

1.1.2.tar.gz) in Ubuntu 8.04. Step 2: extract source codes. Step 3: please check the path of toolchain arm-elf-* is in PATH.

The toolchain arm-elf-* will be used in the compilation.

Tips: The include/configs/ directory under U-Boot source directory contains

configuration files for supported boards. It defines the CPU type, the peripherals and their configuration, the memory

mapping, the U-Boot features that should be compiled in, etc. For instance of PXA270, U-boot will be copied to 0xA3F80000 when it is loaded by

CPU and it uses 0x00020000 to 0x0003FFFF as the boot parameters.

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U-Boot Compilation (2/2) Step 4: compile U-Boot.

U-Boot must be configured for the target board before being compiled, i.e., make <target board>_config, where <target board> is the name of the configuration file in include/configs/, without the “.h”. E.g., Create_XScale_PXA270 is for our target board.

% cd u-boot-1.1.2 % make mrproper

This command often uses to clean all the object files and configurations. You can see Makefile and check what it has done.

% make Create_XScale_PXA270_config % make

The resulting u-boot.bin is the bootloader we want so that we can copy it to PXA270.

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Memory Layout of PXA270

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0xA0000000

0xA4000000RAM

U-Boot

Flash

0x00000000

0x00040000

0x00080000diag

0x00480000

0x01380000

Linux kernel 1

Root Filesystem

0x00020000U-Boot parameters

0x02000000

0x01C00000Linux kernel 2 U-Boot

0xA3F80000


Configure U-Boot If you want to change default configuration for PXA270, you can modify

the specified files and recompile U-Boot. % cd u-boot-1.1.2 % nano include/configs/Create_XScale_PXA270.h

CONFIG_SERVERIP: host system IP. CONFIG_IPADDR: target system IP. CONFIG_BOOTARGS: boot arguments. CONFIG_BOOTCOMMAND: boot command. CONFIG_BOOTDELAY: U-Boot delay (do not set to 0!). CONFIG_LINUX: Linux kernel start command. etc.

Tips: The U-Boot environment variable “bootargs” is used to hold the parameter

options passed to the Linux kernel, as the kernel’s command line parameters.

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Build Your Own U-Boot (1/2) Step 1: please modify the boot command in U-Boot.

CONFIG_BOOTCOMMAND = “run linux” CONFIG_LINUX = “bootm 80000”

Step 2: please try to change the command prompt and display with your group id.

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Build Your Own U-Boot (2/2) Step 3: copy the uImage provided in lab4 to flash address 0x01C00000.

The erased end address is 0x1FFFFFF (32 sectors). Step 4: compile your U-Boot and copy to flash address 0x00000000.

Make sure you also erase the boot parameters sector (0x00020000 to 0x0003FFFF), or your modified settings could not work.

Step 5: reset PXA270 and then you will see new configuration. Try to do some settings so that you can choose which to boot on, the two Linux

kernels ,or the program diag.

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Linux Kernel Version Numbering After the 1.0 release and prior to version 2.6, the number was composed

as “A.B.C”, where the number A denoted the kernel version, the number B denoted the major revision of the kernel and the number C indicated the minor revision of the kernel.

In 2004, after version 2.6.0 was released, the kernel developers no longer uses this system, instead now simply incrementing the third number, using a fourth number as necessary.

In 2011, the kernel version was bumped to 3.0 for the release following 2.6.39, to commemorate the 20th anniversary of Linux.

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Reference: wikipedia – Linux kernel http://en.wikipedia.org/wiki/Linux_kernel

http://en.wikipedia.org/wiki/Linux_kernel


Linux Kernel Compilation (1/2) Step 1: download Linux source codes (mt-linux-2.6.15.3.tar.gz) for

PXA270. Step 2: extract the source codes. Step 3: apply the patch.

% cd pxa270/create-pxa270 % Link http://140.112.90.160:5000/fbsharing/nq8uCcwT to download

patch file % patch -p0 < linux-2.6.15.3-creator-pxa270.patch

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http://140.112.90.160:5000/fbsharing/nq8uCcwT


Linux Kernel Compilation (2/2) Step 4: configure the Linux kernel (check Lab4’s arm-unknown-linux-gnu-*

toolchain path in PATH). % cd ../linux % make mrproper % make creator_pxa270_defconfig The “make <platform>_defconfig” command will create .config by the

default symbol values from arch/<platform>/configs/<platform>_defconfig.

Step 5: compile Linux kernel. % make

The resulting zImage in arch/arm/boot is the compressed kernel image we want.

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Linux Kernel Configuration (1/2) The Linux kernel build system (Kbuild) includes support for a variety of

configuration methods, the most commonly used method is: % make menuconfig

Please install libncurses5-dev package in Ubuntu. Make sure your screen is large enough to display the configuration.

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Linux Kernel Configuration (2/2) Many features and drivers are available as modules, and they are possible

to choose whether to build features into the kernel. Please always build into the kernel, i.e., <*>, in our Labs.

Once the kernel has been configured, you can quit the kernel configuration menu via Esc key or the Exit menu item. Choose “Yes” to save the new configuration into a new .config file.

You can use “ls -a” to check the file.

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built-inmodule


Memory Layout of PXA270 (1/3) The Creator XScale PXA270 board has 32MB flash and 64MB SDRAM.

Flash memory address range: 0x00000000 to 0x02000000. SDRAM address range: 0xA0000000 to 0xA4000000.

Recall that U-Boot has determined the location of kernel image.CONFIG_BOOTCOMMAND "run linux"CONFIG_LINUX bootm 80000

The locations and sizes of kernel image and root filesystem are also determined by Linux kernel (in arch/arm/mach-pxa/mach-creator-pxa270.c).

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Memory Layout of PXA270 (2/3)

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0xA0000000

0xA4000000RAM

U-Boot

Flash

0x00000000

0x00040000

0x00080000diag

0x00480000

0x01380000

Linux kernel 1

Root Filesystem

0x00020000U-Boot parameters

0x02000000

0x01C00000Linux kernel 2 U-Boot

0xA3F80000


Memory Layout of PXA270 (3/3) Based on the memory layout, we can configure our Linux kernel.

static struct mtd_partition creator_pxa270_partitions[] = { ... },{ name: "Kernel", offset: 0x00080000, size: 0x00400000, // 4M mask_flags: MTD_WRITEABLE },{ name: "Filesystem", offset: 0x00480000, size: 0x00F00000, // 15M } ...

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Convert to U-Boot Bootable Image (1/2) We use U-Boot as the bootloader on PXA270, we need to convert the OS

kernel image vmlinux (which zImage is compressed by) to U-Boot bootable image (uImage).

Step 1: get raw binary file. % arm-unknown-linux-gnu-objcopy -O binary -R .note -R .comment -S arch/arm/boot/compressed/vmlinux linux.bin

Step 2: compress kernel image (optional). % gzip -9 linux.bin

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Convert to U-Boot Bootable Image (2/2) Step 3: download mkimage. Step 4: add header.

% chmod +x mkimage % ./mkimage -A arm -O linux -T kernel -C gzip -a 0xa0008000 -e 0xa0008000 -n "CSL Lab5 Kernel" -d linux.bin.gz uImage

If you skip step2, please use -C none and -d linux.bin. mkimage is in the tools folder of U-Boot source codes.

You can see the mkimage usage by executing without arguments. The resulting uImage is the U-Boot image we want.

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Test Your Linux Kernel (1/2) Please refer to Lab1 to copy new Linux kernel and root filesystem to flash. Step 1: download new 15M rootfs (root filesystem). Step 2: copy your uImage to flash. Step 3: copy new rootfs to flash. (take about 7 minutes) Step 4: reset PXA270, now you can see your own Linux kernel is booted

(the message “CSL Lab5 Kernel”). Please use “df -h” to check the size of filesystem.

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Test Your Linux Kernel (2/2) However, the driver of the network card on PXA270 does not be

configured in default Linux configuration. Please try to configure the driver and build it into your kernel.

Please use “ifconfig eth0” to check that your network card works.

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Lab Requirement Show your own command prompt in U-Boot. Show that you can choose what to boot on, and it is as simple as possible. Show that you can use “tftp” on your Linux kernel which has a 15M

filesystem. Please hand in your lab report to the FTP.

Server: 140.112.90.174 Username: csl2015 Password: csl2015HomeWork Directory: lab5,6 Please use this format for filename: “G# Ver#”, where G# is your group id and

Ver# is revision version number. E.g., G1 Ver2

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